1. Field of the Invention
The present invention relates to a device for positioning an object. The device can be used, for example in an exposure apparatus. The invention also relates to an exposure apparatus having the device.
2. Description of the Related Art
A scanning exposure apparatus usually has a stage device that moves a reticle. Some suggestions have been made for a driving mechanism of the stage device so as to improve the throughput of the exposure apparatus.
FIG. 13A shows a stage device suggested in Japanese Patent Laid-Open No. 2004-079639. A reticle stage 104 has a reticle 103 placed thereon and moves in a scanning direction (Y direction). Linear motors are provided on both sides of the reticle stage 104. The linear motors include movers 105 fixed on both sides of the reticle stage 104 and each having a permanent magnet, and stators 106 fixed to a base (not shown) and each having a plurality of coils.
In addition, repulsive movers 107 are provided at front and back sides of the reticle stage 104 in a movement direction thereof, and repulsive stators 110 are provided at both ends of a movement stroke of the reticle stage 104. The repulsive movers 107 and repulsive stators 110 have permanent magnets, whereby the reticle stage 104 can be accelerated or decelerated using repulsive forces generated between the permanent magnets of the repulsive movers 107 and those of the repulsive stators 110.
FIG. 13B is an illustration showing the repulsive mover 107 and repulsive stator 110. The repulsive stator 110 includes a pair of permanent magnets 112 disposed such that the N-pole of one of the permanent magnets 112 faces the S-pole of the other, and yokes 113 that allow magnetic flux to circulate between the pair of permanent magnets 112 via lateral sides. The repulsive mover 107 includes a permanent magnet 109. When the repulsive mover 107 is located at a position indicated by a dotted line, like poles of the permanent magnet 109 and one of the permanent magnets 112 face each other, whereas like poles of the permanent magnet 109 and the other one of the permanent magnets 112 face each other. Using repulsive forces between the permanent magnets 112 and 109, a force can be applied to the reticle stage 104 from either end of the movement stroke of the reticle stage 104. With such a configuration, the reticle stage 104 is driven while preventing the coils (106) from being heated due to driving of the linear motors.
In such a configuration in which a force is applied to a stage by using a repulsive force from permanent magnets, magnetic flux may be noticeably scattered and leak to the surrounding when the repulsive force is generated. In particular, a stage device with a high acceleration may cause large leakage flux, and thus, magnetic substances provided around the stage may be attracted.
In many cases, a measurement sensor and a processing unit may be arranged around a stage device. If these components and members for supporting these components are attracted by the leakage flux, positioning accuracy of the stage and processing accuracy of an object placed on the stage may be decreased. In particular, an exposure apparatus has an illumination optical system, a projection optical system, and the like, arranged around a stage device. If supporting members of these systems are magnetically attracted, exposure accuracy may be decreased.